ENCINAL — Buck Russel parked his vehicle along the train track, hopped out and stopped to see evidence of what had happened weeks before along this stretch of Union Pacific rail line, where a freighter truck ripped out one of the train crossing planks.

But Russel, a locomotive engineer and safety coordinator for Union Pacific’s San Antonio service area, also noticed skid and gouge marks in the street where the asphalt meets the train tracks, indications that other trucks had dragged or hooked into the tracks.

An oil drilling boom in the Eagle Ford shale formation has meant big business and more freighter truck traffic in South Texas, especially along Interstate 35.

That upsurge isn’t just causing more congestion on the roads — it’s also increasing the number of times trucks cross train tracks, because one of Union Pacific’s main lines runs parallel to I-35.

Today, UP is launching a bilingual railroad safety billboard campaign along the interstate between San Antonio and Laredo, targeting commercial truck drivers who are most likely to cross paths with a locomotive.

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The campaign features six billboards in both directions, near Pearsall, Dilley, Cotulla and just north of Laredo.

“It’s just booming out there, and we’re trying to figure out how do we reach the truck drivers in the cab,” said UP Spokeswoman Raquel Espinoza-Williams.

In 2010, Union Pacific recorded six collisions with its trains along the I-35 corridor. None were fatal.

Russel wants to keep it that way.

“It’s imperative that we prevent that from happening down here,” he said.

The average train weighs 12 million pounds, travels at 60 miles per hour and takes a mile or more to stop, and that’s if the engineer is forced to hit the emergency brake.

Truck traffic is also increasing over tracks that cross private drives, because they may be the only access points to drilling sites.

UP officials worry the trucks might not have enough vertical clearance — the distance between the bottom of their trailers and the tracks — to safely cross these tracks, especially because roads weren’t designed for heavy traffic, Espinoza said.

Russel has reached out directly to the drilling companies, including Chesapeake Energy, which has 17 drills in the Eagle Ford shale, a number expected to grow to 30 by year’s end, said spokesman Silver Vasquez.

Chesapeake has made an effort to work with UP and its truck drivers. It hires a UP flagman to help direct truck traffic whenever the freighters are hauling heavy equipment over the tracks, Vasquez said.

“All we try to do is to make sure that they know the terrain, know where they’re driving and follow best practices,” Vasquez said. Russel knows that the economic boom caused by the drilling is good for a lot of companies, including Union Pacific itself. Some of the oil companies are UP customers.

Like it or not, the economic and accompany truck activity aren’t going anywhere soon, which means Russel has his work cut out for him.

Just after examining the skid marks on the road at Encinal, an endless stream of freighters passed over the tracks. One of them briefly backed up back over the track to make room for another freighter and stalled on the track for at least 20 seconds.